The medulla oblongata, located in the hindbrain, is responsible for regulating involuntary activities like heartbeat, breathing, and blood pressure. It ensures that vital functions continue automatically without conscious control. The cerebrum controls voluntary actions, while pons and midbrain perform other specific functions. Therefore, the correct combination is Blood pressure: Medulla in hindbrain, as this region coordinates and maintains the rhythmic functioning of the heart and lungs, ensuring a steady flow of blood throughout the body. The correct option is (D).